Method of preparing a plastic sheet



April 22, 1952 R. R. BECKHAM 2,593,405

METHOD OF PREPARING A PLASTIC SHEET Filed July 50, 1949 5 Sheets-Sheet l 3nnento1' April 22, 1952 R. R. BECKHAM METHOD OF PREPARING A PLASTIC SHEET 3 Sheets-Sheet 2 Filed July 30, 1949 April 22, 1952 R. R. BECKHAM METHOD OF PREPAR'INGA PLASTIC SHEET Filed July 30, 1949 3 Sheets-Sheet 3 Ihmentor .straight nor horizontal.

Patented Apr. 22, 1952 UNITED STATES PATENT OFFICE METHOD OF PREPARING A PLASTIC SHEET Robert R. Beckham, Toledo, Ohio, assignor to Libbey-Owens-Ford Glass Company, Toledo, Ohio, a corporation of Ohio Application July 30, 1949, Serial No. 107,730

The present invention relates generally to the reduction of sun and sky glare, and more particularly to a novel curved and angled, laminated glass window, windshield or the like that is provided with a built-in glare-reducing portion; and I to an improved method of producing such a device.

at the top to practical extinction at the bottom,

laminated with one or more sheets of glass which have a relatively high luminous transmittance in the visible region of the spectrum, but which may have relatively low ultra-violet light transmittance.

The procedure for dyeing the plastic interlayer as disclosed in the Ryan-Mattimoe application, in which the plastic is dyed in the flat and then cut to size, has proved entirely satisfactory for dyeing the glare-reducing portions .of the interlayer for flat Windshields, for most two-piece Windshields, and for those that are curved in the vertical plane, but which have a very slight or no curve in the horizontal plane; and for these types of Windshields such a dyeing procedure produces a straight horizontal cut-ofi line between the dyed and undyed areas when 1 the windshield is mounted in an automobile. However, considerable diificulty is encountered in achieving a proper cut-off line when dyeing interlayers for bent Windshields, and particularly for one-piece bent Windshields, which have their principal bent curvature in the horizontal plane,

which have an outline that is curved at the'top and bottom and has diverging sides, and which "are mounted in the automobile at an angle to the vertical.

When interlayers for this type of windshield are dyed in the fiat, cut to the shape of the glass,

sandwiched between the two pieces of bent glass and the laminated unit then mounted in an automobile, it is found that the cut-off line at the bottom of the dyed area will neither be Instead, it will appear in the windshield as a line which curves rather sharply downward at the two opposite ends of the windshield, and this is unsatisfactory, first 10 Glaims. (CI. 18-56) because the end curves run into the viewing area and, second, because it is undesirable in. appearance.

It has been suggested that this diffilculty be corrected by mounting the plastic interlayer in a frame, that is bent to the shape of the finished windshield, and then dipping it into the dye bath with the shaped frame held at the same angle as the windshield is to be mounted at in the car. However, this presents a number of practical difiiculties when continuously dyeing a large number of plastic sheets in commercial production, and in satisfactorily rinsing the dyed sheets to insure a uniform, unstreaked, and properly graduated tinted or shaded area with a sufficiently imperceptible fade-off from the dyed to the undyed areas.

Now it is an aim of the present invention to overcome all of these difliculties and still provide an interlayer for Windshields of the above shape and form, having a dyed area whose cutoff line will appear to the observer to follow a straight, horizontal path.

Briefly stated, this is accomplished according to the invention by first dyeing the plastic sheet in the flat according to accepted procedures, and then distorting or shaping the flat dyed plastic in such a manner that when it is incorporated into a windshield by laminating with two sheets of glass that are bent in the horizontal plane, and the composite structure then mounted at an angle in an automobile, the bottom or cut-off line of the dyed area of the plastic will appear as a straight, horizontal line to the driver and occupants of the car.

Another object is the provision of a novel method for dyeing, and then shaping or distorting the dyed plastic to produce a plastic interlayer for a windshield of the above general character that will have a cut-off line of the desired shape and angularity.

Other objects and advantages of the invention will become more apparent during the course of the following description, when taken in connection with the accompanying drawings.

In the drawings, wherein like numerals are employed to designate like parts throughout the same:

Figure 1 is an elevation of the windshield of i the invention as viewed from the interior of an automobile in which it is installed;

Fig. 2 is a vertical sectional view through the windshield arranged in the angled position which it occupies in the automobile;

Fig. 3 is a perspective plan view of two sheets straight, horizontal line.

3 of glass and a dyed plastic interlayer prior to assembly into a sandwich and laminating into a finished windshield;

Fig. 4 is an elevation of one form of apparatus designed for dyeing and rinsing a plastic sheet that is to be shaped and cut into the shaded interlayer for the windshield;

Fig. 5 is a perspective view of the flexible dyeing frame for the plastic sheet;

Fig. 6 is an enlarged fragmentary view of one side of the dyeing frame, showing the hinged corners in detail;

Fig. 7 is an elevation of the shaping frame for distorting the flexible dyeing frame to shape or reshape th plastic sheet after dyeing; Fig. 8 is a section taken substantially on the line 8-8 in Fig. 7;

Fig. 9 is a section taken substantially along the line 9-9 in Fig. 7;

Fig. 10 is an enlarged, fragmentary view of one corner of the shaping frame;

.can be dried; and V Fig. 14 is a diagrammatic view showing'in phantom lines, a plastic sheet in its normal form 7 after it has been dyedin the flat and, in full lines,

theform of the sheet after it has been distorted -to the desired shape.

Referring now more particularly to the drawings, there is illustrated in Fig. l a windshield l0, produced in accordance with this invention, as it appears from the front seat of an automobile ii in which the windshield is mounted. As explained above, this windshield is of conventional laminated construction in that it comprises two sheets of glass l2 and i3 and a non-brittle plastic interlayer M (Fig. 2'). However, it departs from the ordinary construction by being specially shaped, and by having its plastic interlayer I l provided with a glare-reducing area or band [5 which is colored or of a neutral shade and graduated in intensity from relatively darlcat the top to practical extinction at the bottom, ending-in ,an almost imperceptible cut-off line [6 between I the colored or shaded and uncolored or unshaded areas. v

The purpose of this is to provide, within the windshield, a glare-reducing area in which the color or neutral shade is relatively deep or intense at the top of the windshield, which is the area presenting the greatest glare, and tapers ofi gradually to a very low intensity, or to no shade or color at all, as it approaches the essential sighting area ll of the windshield.

It'will be noted from Fig. 1 that to the eye of an observer in the car the cut-off line 5- of the colored or neutral shaded area [5 appears as a However, this is not actually the case, and I have discovered that .in the specially curved, shaped and angled windshields now coming into common use in the modern streamlined and revolutionary designs of automobiles proposed for, and currently on, the market, a cut-off line in the dyed area ofthe plastic interlayer that is actually straight and horizontally arranged willnot appear-to be so when laminatedwith the glass sheets and mounted in the automobile. Consequently, a dyed area which actually has a straight cut-off line cannot be used. Instead, it becomes necessary to.

produce a dyed area having a cut-off line which, regardless of its form when the plastic sheet is in the flat, is designed to appear as a straight, horizontal line when the dyed plastic has been laminated into a windshield and the windshield mounted at an angle in an automobile.

Thus, in the windshield Ill of Figs. 1 to 3, and

which is characteristic in shape, contour and angled position to the newer modern designs, it will be seen from Figs. 1 and 2 that, in order to obtain the straight horizontal effect of cut-off line seen in Fig. 1, it has been necessary to provide a dyed area having a cut-off line that is actually not straight at all, and so cannot be horizontally arranged; Instead, as best seen in Fig. 3, the cut-off line [3 is actually curved and is somewhat similar in contour to the curvature of the top lines of'the glass sheets 12 and I3. Now the dyeing of a plastic sheet in a manner to produce a glare-reducing portion of this form that is properly graduated in color or shade from top to bottom, and which has an almost imperceptible cut-off line, presents a considerable problem.

Nevertheless, I have discovered a novel and yet relatively simple way of accomplishing it, which has the distinct advantage of permitting the plasticto be dyed in the flat, with the flat ing made up of four metal frame sections or rails 20, 2 I, 22 and 23 which are hinged or pivoted together at the four corners of the frame as shown at 24. The two side rails 29 and 21 are of rigid construction, while the bottom and top rails are flexible or bendable; and the top rail 23 is preferably longer than the other three rails and extends outwardly beyond the side rails 20and 2| as shown at 25 to facilitate hanging of the frame during the dyeing, rinsing and drying of the plas- -.tic. 1

f- The plastic sheets It may be secured to the frames 19 in any desired manner, but I prefer to adhere them to the frame by first coating one side surface of each of the four rails 20 to 23 of the frame with a plastic solvent such as ethylene glycol mono-butyl ether and then smoothing the marginal portions of the plastic sheets into full contact with the frame entirely around their perimeters.

With a plastic sheet l8 mounted on the frame [9, a marginal portion thereof may be dyed in any desired manner, and there is illustrated in Fig. 4 one form of apparatus which is satisfactory for the purpose. The apparatus of Fig. 4 includes a framework 26 made up of a pair of horizontally arranged beams 21, supported on vertical floor beams 28 and connected together by bridging members 29 extending transversely thereof and also secured to the upper ends of opposed floor The framework 26 substantially surrounds and acts to support certain of the elements of a loading section A, a clipping section B and first and second rinsing sections C and D respectively.

In order to permit the plastic sheets to be moved progressively through the various sections of the dyeing apparatus, .rails 30 are mounted on the inner faces of the beams 21, which rails are adapted to support wheels 3| from which. are suspended carriages 32 provided with hooks 33 adjacent their opposite ends.

Within the dipping section B the rails 36 are cut out as shown at 34, and normally positioned within this cut-out area is a dipping elevator 35 which carries rails 36 adapted to align with the rails to close the cut-out portion 34 and provide a continuous track when the elevator is in raised or normal position. The elevator is carried at the lower end of a piston. rod 31 whose upper end is-attached to a piston 38 mounted for reciprocal movement within an air or hydraulic cylinder 39. v Also mounted within the dipping section B, on a platform 46, and in vei'ticalalignment. with the elevator 35 is a vat or tank 41- containing a dye bath, which is preferably a solution of a suitable dye, for example 2% of 1:4bis ortho-sulpho-parw tolyl aminoanthraquinone in a by volume mixture of aqueous denatured alcohol.

' To initiate the dyeing procedure, a; flexible frame I9 to which has been secured a sheet of plastic 18 is hung from the hooks 33 of a carriage 32, positioned within the loading. station A, by means of the extensions 25 on the toprail of the frame. The carriage 32, carrying the framed plastic is then moved to the right into thedipping section B at which time the wheels 3 i of the carriage 32 will be riding upon the rails 36 of the elevator 35.

Air or liquid is then introduced into the upper end of the cylinder 39 through a pipe 42 to move the elevator 35 quickly downward into the broken line position in which the plastic sheet is just above the dye bath. The elevator 35 is then moved slowly downward to dip the lower marginal portion of the plastic sheet I8 into' the bath in accordance with a predetermined time cycle that will produce the desired graduation in depth of color from the bottom of the dyed area to the top thereof. As soonas the plastic sheet has been immersed in the dye bath for the proper distance to give the width of dyed area desired, fluid is introduced into the lower endof the cylinder 39 through a pipe 43 to quickly raise-the elevator 35 into the full line position and thus withdraw the plastic from the dye.

Since at this time the rails 36 on the elevator 35- areagain in alignment with the rails 30, the carriage 35 can again be moved to the ri'ghtto transfer the dyed plastic-sheet! B'lromthe dipping section B to the first rinsing section C.

Within the rinsing section C the dyed portion of the plastic sheet is immediately rinsed with a water-soluble alcohol-water mixture, such asone made up of 50% denatured ethanol and 50%- by volume of distilled water, to remove the dyeing solution from the plastic and to arrest thedyein'g:

action. It is important that thisv be doneover the entire area of the dyed plastic 'as'ra-pidly-"as possible and to this end there is providedwithin the rinsing section C a pair of carriages and 45 mounted on wheels 46 which are adapted to run on a horizontal track 41. Each of the/carriages 44 and 45 carry pairs of vertical'pipes 48 provided with angled nozzles '49 and which are positioned to lie with one nozzle on either side of the plastic sheet 13 as the carriages are moved along the track 41.

The carriage 44 is attached by means of 'a'link 56' to the upper run of a chain 5ltrained about sprockets 52 carried by shafts 53; while the car-- riage 45. is. attached 'to the lower run 'of thechain 6 5! by a link 54. A handle 55 is keyed to a shaft 56 which carries a gear 51 adapted to mesh with a corresponding gear on the'shaft 53. By turning the handle 55 in a clockwise direction the chain 5| will be driven to cause the carriage 44 to move to the right and the carriage 45 to move to the left. This movement will cause the carriages 44 and 45 to move toward one another and rinsing solution fed to the pipes 48 will thus be sprayed on both sides of the dyed plastic from the ends thereof toward the center. When the carriages 44 and 45 meet, the handle 55 is moved in a counterclockwise direction to move the carriages to' their original "position and thus complete the first I spraying operation.

From the first rinsing section C the carriage 32 is moved into the second rinsing section D' where the dyed portion of the plastic is finally rinsed with distilled water.

This can be accomplished by arranging water pipes 58 in position to lie on either side of the plastic sheet as it is moved into the section D and which pipes are provided with suitable openings through which water can be sprayed onto the pies tic sheet;

Although the dyeing and rinsing procedure have been described above in connection with a single plastic sheet, it will be understood that the carriages 32 can be, and preferably are, made wide enough, and supplied with suffioient hooks, 33 to accommodate a plurality of sheet carrying frames side by side on a single carriage, and that in this way a larg number of plastic sheets can be'proc essed at the same time.

After rinsing, the frames l9 carrying the dyed sheets are placed in a drying oven for a relatively short time (usually about 10 minutes) to remove the surplus rinsing materials from the plastic sheet.

This preliminary drying may be performed in a tunnel type drying kiln such as shown in Fig. 13 by mounting the frames I8 on a carriage 55 mounted on wheels 60 to run along tracks 6| on the floor 62 of the kiln 63. The kiln 63 is preferably heated, as by electrical resistance units 64 and air may be blown into the kiln, past the heating units 64 and toward the plastic sheets, through a pipe 65 to circulate the heat and speed up the drying action.

Following the preliminary drying of a dyed plastic sheet [8, it is then, while still adherently supported on the flexible frame l9, ready to be distorted into a form that will provide a dyed portion I5 of the proper shape and having a-cut-oil line. 16' of the desired path. Accordin to one preferred form of the invention this can be done on a shaping frame 66 such as is illustrated in Figs. 7 to 12.

As there shown, the frame 66 is of open rectangular shape, being made up of four angle iron sections 61, 68, 69 and IE, welded together at their meeting ends and provided with angularly extending bracing members I I. The top and bottom sections 61 and 68 of the frame 66: are provided on their outer faces, midway their ends with spaced, grooved slide members 12 within and between which is slidably received a fiat bar 13 having a flange 14 at its upper end that extends rearwardly over the section 61. The flange 14 is provided with a threaded vertical opening 15 within which is received the threaded end of a bolt I6 whose lower end is rotatably mounted in an opening 11 in the lateral flange of the section 61 by means of areduced'portion 1'8 andcollars ld'on the'bolt 16. By this means the bar 13 may be moved vertically within the slides 12 by rotation of the bolt 16 for a purpose to be more .clearly .hereinafter set forth. 1

- In order to mount the flexible frame [9 upon the shaping frame 86 and to support it thereon .during distorting of the plastic sheet i8 carried thereby, there are screwed on the sidesections 69 and 10 of the frame 66, adjacent their ends, rectangular stop blocks 85 which are provided with frame rail receiving grooves 8i; while screwed to the top sections 61 and 63, adjacent their ends are substantially U-shaped frame rail retaining members 82 and 83 respectively. For the purpose of distorting the frame [9, when it is on the shaping frame 66, to reshape the plastic sheet, there are secured to the bar 13, adjacent its opposite ends, substantially L-shaped plates 34 having the top surface 85 of the horizontal leg of the L angled downwardly and inwardly to prevent slipping of the frame from the plate.

' In distorting the plastic sheet I8 to the desired shape, the frame [9 containing the sheet is mounted on the shaping frame 66 while the bar 13 of the latter is in the lowered position shown in Fig. 7 and at which time the uppermost point vof the top surface 85 of the horizontal leg of the L-shaped plate 83 is in substantial alignment ,with the bottoms of the grooves in the U-shaped retaining blocks 83. When properly mounted on the shaping frame 66, the bottom rail 22 of the frame [9 will rest in the grooves in the blocks 83 and its center portion will rest against the surface 85 of the lower plate 8 2 on the bar 13; the side rails and 2| will lie in the grooves 8! of the stop or locator blocks 80; and the top rail will rest upon the face 85 of the upper plate 84 on the bar 13, all as shown in broken lines in Fig. 12.

Deformation of the flexible frame I9 and corresponding distorting or shaping of the plastic sheet carried thereby is then accomplished by rotating the bolt 16 to raise the bar 13 within the slides 12, causing the plates 84 to bend the rails23 and 22 upwardly, until the frame 49 is in the position shown in full lines in Fig. 12. When this has been done it will be noted that the side rails 20 and 2| have been moved inwardly out of contact with the blocks 86; that the top and bottom rails 23 and 22 respectively have been bowed or arched; "and that the bottom rail 22 has moved out of the groove in the blocks 83 while the top rail 23 has moved into contact with the top of the curved or angled grooves 86 in the blocks 82. Thus, the blocks 82 act as stops to control the distance that the bar 13 will be moved upwardly, and to also control the amount of distortion of the frame I9.

For this reason, blocks should be used at 82 which have grooves of the angle or curve that it is desired to have the rail 23 assume at those points. Or, if desired, the blocks 82 may be provided with slots for the machine screws 8'! which will permit the grooves 86 to be adjusted to the desired angle. The feature of hinging or pivoting the rails of the frame ii) at the four corners is an important one in insuring proper distorting or shaping "of the plastic sheet [8 because, by this means the .top and bottom rails 23 and 22 are permitted because the'u-p'p'er ends of the braces 88 are not securedto therail 23 in any way, this top rail is free to move away therefrom during distortion of the hall e as clearly shown in broken lines in Fig. 6.

.It will be seen from the full line showing in Fig. 12 that afterfdistortion or bending of the frame '19 in the manner described above, the plastic sheet l8 will be so shaped that, when turned .bott'omside up, it will exhibit a dyed area, 45 of the shape and form shown in the interlayer. 'fi of.Fig. 3, and havinga cut-off line l6 following. the trace or path required in the interlayer of that-figure for the particular shape, contour and angle of windshield shown in Figs. 1 and 2=to give a straight, horizontal cut-off line when mounted at an angle in an automobile. This is shown diagrammatically, but somewhat more clearly in Fig. 14 where the broken lines show the plastic sheet i8 after it has been dyed ing the reshaped plastic, is placed on the carriage 59 in the drying oven or kiln 63 where it is dried at elevated temperatures (preferably around F.) for a sufiicient length of time to remove all solvents absorbed from the dye bath and all adsorbed moisture (not more than .5% must be permitted to remain). 1

' The distortion or strain in the plastic during reshaping maycause some wrinkling of the distorted sheet. However, since the plastic shrinks endwise during drying these wrinkles will pull out in the drying oven.

3 After drying, the plastic is cooled down to room temperature while still held in its distorted shape, and this acts to freeze the strains in the sheet. It may then be removed from the frame I9 and itwill be found that it will retain the shape into which it has been distorted. Nevertheless,

. because the material of the sheet l8 has elastic memory, that is, an inherent tendency to return to its natural state after deformation, there may be a slight spring back when it is first removed from the frame. However, this is usually so slight as to be unobjectionable or, it can be compensated for byover distorting if desired.

Although the distorted, dyed and cooled plastic will quickly resume its original shape at elevated temperatures, and ultimately even at room temperature, I have found that, after the first spring back, it will maintain its strained or distorted shape forseveral days at ordinary room temperatures, and this is suflicient for the present purpose.

Following removal of the plastic sheet l8 from the frame is, it is trimmed to size to form an interlayer l4, thus removing the marginal portions that have been adhered tothe frame. It is then assembled together with two pieces of glass as shown in Fig. 3 to form a glass-plastic sandwich which is then laminated under heat and pressure to form a composite, unitary structime which can be used as a windshield l0 and which, when mounted inan automobile inthe manner shown in Figs. 1 and 2, will exhibit a dyed non-glare area l5 having a straight, horizontalcut-off line. I Once the interlayer M has been laminated between two sheets of glass it will be permanently held in its strained shape and no ill effects will be had. However, according to a somewhat modified form of the invention, an interlayer of the same shape and having the same dyed area as shown at i l, but which is unstrained, can be produced. This is accomplished by pattern cutting the plastic to the shape shown at :4, then mounting it on a flexible frame which has been constructed to fit the pattern out shape, next distorting the frame to reshape the plastic into rectangular shape, heating the reshaped plastic to remove wrinkles, dyeing the plastic while still in the rectangular shape in the flat, and finally releasing the distorted frame to permit it and the dyed plastic to assume their original shape (as shown at M) and then drying in the oven before removing the plastic from the frame.

Although the present invention has been described in connection with a windshield of particular shape and that is set at a particular angle in the automobile, it will be obvious that dyed plastic interlayers may be produced by the teachings of this invention to fit into any type of curved and angled windshield and to still exhibit a colored or neutrally shaded glare-reducing area having a straight, horizontal cut-off line.

In fact, it is to be understood that the forms of the invention herewith shown and described are to be taken as illustrative embodiments only of the same, and that various procedural changes may be resorted to without departing from the spirit of the invention or the scope of the subjoined claims.

I claim:

1. In a method of preparing a plastic sheet having at least one substantially straight edge to present a predetermined appearance when laminated as an interlayer between sheets of glass and mounted as part of a windshield in an automotive vehicle, the steps of dyeing a marginal portion of said sheet that is adjacent said substantially straight edge, distorting said dyed sheet into a shape in which the formerly substantially straight edge adjacent the dyed margin assumes a generally bowed contour, and first drying the dyed sheet at elevated temperatures and then cooling the same to room temperature while still holding it in its distorted shape.

2. In a method of treating a plastic sheet having two substantially straight opposite edges to be used as an interlayer in laminated safety glass, the steps of dyeing a marginal portion of said sheet that adjoins one of said substantially straight edges, rinsing the surplus dyeing material from said sheet, distorting said dyed and rinsed sheet to a shape in which the edge adjoining the dyed margin assumes a generally concave bow and the opposite edge assumes a generally convex bow, heating said sheet to dry the same and then cooling the heated sheet to room temperature all while still holding said sheet in its distorted shape.

3. In a method of treating a substantially quadrilateral plastic sheet prior to laminating, the steps of dyeing a portion of said sheet while it is in its natural shape, and then distorting said sheet into a shape having two opposite :idges bowed in substantially the same direc- 4. In a method of treating a plastic sheet having at least one substantially straight edge prior to laminating between sheets of glass, the steps of dipping said sheet into a dye, rinsing the surplus dye from said sheet, partially drying said sheet to remove the rinsing material, distorting said dyed, rinsed and partially dried sheet to a shape in which said formerly substantially straight edge assumes a generally bowed contour, and then thoroughly drying said sheet at elevated temperatures and finally cooling the dried sheet to room temperature all while still holding said sheet in its distorted shape.

5.In a method of preparing a plastic sheet having a substantially straight edge to present a predetermined appearance when laminated as an interlayer between sheets of glass and mounted as part of a windshield in an automotive vehicle, the steps of dipping a marginal portion of said sheet adjoining said substantially straight edge in a dye solution, rinsing the dyed sheet with a water-soluble alcohol-water mixture, rinsing the dyed and preliminarily rinsed sheet with water, partially drying said sheet at elevated temperatures to remove the surplus water, distorting said partially dried sheet to a shape in which said substantially straight edge assumes a convex bow, then thoroughly drying the sheet at elevated temperatures, and finally cooling said sheet to room temperature, said last two steps being performed while said sheet is held in its distorted shape.

6. In a method of treating a substantially quadrilateral plastic sheet prior to laminating, the steps of mounting said sheet on a frame of a similar shape provided with flexible rails, dyeing a portion of said sheet while in its natural shape on said frame, and then bowing two opposite rails of said frame in the same direction to distort said sheet into a different shape.

7. In the production of laminated safety glass embodying two sheets of glass and an interposed sheet of plastic material bonded to the glass sheets to form a composite structure, the method of preparing a plastic sheet having at least one substantially straight edge to present a predetermined appearance when laminated as the interlayer between the sheets of glass and mounted as part of a windshield in an automotive vehicle, comprising coloring a marginal portion of said plastic sheet that is adjacent said substantially straight edge, and distorting the colored sheet in the plane of said sheet into a shape in which the formerly substantially straight edge adjacent the colored marginal portion assumes a generally bowed contour prior to laminating the colored and distorted plastic sheet between the sheets of glass.

8. In the production of laminated safety glass embodying two sheets of glass and an interposed sheet of plastic material bonded to the glass sheets to form a composite structure, the method of preparing a substantially quadrilateral plastic sheet to be used as the interlayer between the two sheets of glass, comprising coloring a portion of said plastic sheet along a marginal portion thereof while said sheet is in its natural shape, distorting the colored sheet in the plane of said sheet into a shape having two opposite edges bowed in the same direction, and heating the colored sheet while maintaining it in the distorted shape prior to laminating the same between two sheets of glass having curved edges 11 that conform substantially to the bowed edges of the plastic sheet.

9. In the production of laminated safety glass embodying two sheets of glass and an interposed sheet of plastic material bonded to the glass sheets to form a composite structure, the method of preparing a plastic sheet having at least one substantially straight edge to present a predetermined appearance when laminated as the interlayer between the sheets of glass and mounted as part of a windshield in an automotive vehicle, comprising coloring a marginal portion of said plastic sheet that is adjacent said substantially straight edge, distorting the colored sheet in the plane of said sheet into a shape in which the formerly substantially straight edge adjacent the colored marginal portion assumes a generally bowed contour, and then heating and subsequently cooling the sheet while maintaining it in its distorted shape prior to laminating between two sheets of glass having curved edges that conform substantially to the bowed edge of the plastic sheet.

10. In the production of laminated safety glass embodying two sheetsof glass and an interposed sheet of plastic material bonded to the glass sheets to form a composite structure, the method of colored material are curved in the same direction.

ROBERT E. BECKHAM.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,574,683 Ogren Feb. 23, 1926 1,687,340 Little Oct. 9, 1928 2,237,567 Land Apr. 8, 1941 2,308,732 White Jan. 19, 1943 2,344,117 Vierling Mar. 14, 1944 2,461,612 Olpin Feb. 15, 1949 OTHER REFERENCES Ser. No. 233,688, Kasemann (A. P. (2.), published Apr. 27, 1943. 

